There exists an urgent need for improved safety features for machine tools, especially for machine tools such as table saws, which overall have an especially grim safety record, dating back more than a century. Each day, consumer-grade table saws cause life-changing trauma injuries in the United States and other nations, including an estimated ten amputations daily in the United States alone. Besides table saws, many machine tools, such as woodworking and metalworking machines including, but not limited to: band saws, drill presses, lathes, shapers, jointers, jig saws, disk sanders and spindle shapers, milling machines and grinders, require the operator to manually move a work piece and/or the operator's hands in close proximity to a cutting blade or to other potentially dangerous elements or features. It is not uncommon for machine operators to inadvertently contact the dangerous element, resulting in a very serious injury such as amputation of fingers or mutilation of hands, resulting in a life-altering disability and much pain and suffering as well, as great financial costs for medical treatment, rehabilitation and lost income. The estimated annual cost of such accidental table saw accidents, in the United States alone, has been estimated to be $2 billion, which places an economic burden on not only the injured persons, but also on employers, manufacturers, retailers, medical institutions, insurance companies and government.
In the US, consumer table saws alone presently account not only for ten accidental amputations daily, but for an aggregate of 35,000 visits annually to hospital emergency rooms, to treat injuries of varying levels of severity.
Over the past decade, there has been great interest in machine operator flesh-sensing, in order to quickly stop a table saw blade if the operator accidentally contacts the spinning blade. Until now, progress in the art has been largely due to the many inter-related patents of GASS, et al., such as U.S. Pat. No. 6,994,004, which have disclosed a method of destructively stopping a saw blade after direct contact between an operator and the saw blade. Although it is expected that the GASS et al. method, of capacitively sensing direct contact between an operator's flesh and a moving blade, will reduce the severity of injury to an operator, it will still likely result in some finite level of injury to the operator. U.S. Pat. No. 7,290,474, issued to KELLER, also discloses destructively stopping a saw blade, through the use of an explosive device. All of the presently available systems, for rapidly disabling a machine tool in case of emergency, have disadvantages of excessive cost, lack of convenience and/or lack of adaptability to previously-manufactured machine tools. Unfortunately, perhaps due to the aforementioned disadvantages, over the past decade, safety systems have not been widely implemented, and the accident statistics related to table saw injuries have shown no discernable improvement.